Questions abound about the Miami Heat’s playoff prospects, despite the stellare regular-season play of guard Dwyane Wade, left, and forward LeBron James. (Evan Vucci/AP)

LeBron James lay on his stomach in the middle of the floor of the Miami Heat locker room as a trainer stretched his legs and feet before a game last Sunday. He convulsed with laughter for more than a minute, his back bobbing, hand slapping the carpet, as he watched repeated replays of Metta World Peace decking James Harden with an elbow during that afternoon’s game between the Los Angeles Lakers and Oklahoma City Thunder.

Dwyane Wade walked over with a microwave-safe container of pasta and a bottle of water and the pair traded estimates about the length of the inevitable suspension, which turned out to be seven games.

“That’s crazy,” James said. “I never seen nothing like that in my life.”

Actually, James has seen plenty while wearing a Heat uniform over the last two seasons, much of it crazy, some of it painful, other parts exhilarating — but little of it amusing. In just over a year, the Heat has evolved from the NBA’s most hated and feared franchise to merely one of the league’s elite teams, a squad whose playoff expectations are enormous — NBA title or bust — but prospects quite uncertain.

Though Miami won the Eastern Conference’s second seed with a 46-20 record, earning the right to face the New York Knicks in a home playoff opener Saturday, concerns abound.

The Heat’s fade in last year’s Finals has not been forgotten. Miami’s struggles on the road, its erratic play during the second half of the lockout-shortened season and recent defeats to quality teams raise questions. And then there are the obvious holes at the edges of its much-celebrated lineup, which features no stellar point guard or center.

“We have a lot of critics,” Coach Erik Spoelstra said. “We talk about that all the time. None of it matters. We know what we’re playing for; we know the journey we have to go on, and we only have each other to lean on. . . . We have to continue to try to improve and try to stay committed to our truth.”

The truth is, the Heat remains as theoretically imposing as it did in the summer of 2010, when James, Wade and Chris Bosh signed free agent contracts to give the Heat an unparalleled Big Three. James arguably has been the game’s most dominant player this season, and Miami has manhandled teams at home, at one point compiling 17 straight victories. Its stars like to play defense. The playoffs are here, and Wade has proven himself one of the biggest big-game performers ever.

James, meantime, has been a more complete and versatile player while putting forth numbers that justify the “MVP!” chants he received at home nearly every time he stepped to the free throw line in the season’s final days.

Yet the backdrop to every early-round success the Heat accrues will be the ghost of its humbling defeat to the Dallas Mavericks in the Finals in six games last year. As Houston Rockets Coach Kevin McHale pointed out this past week, no matter his regular season achievements, James won’t go down as among the historic great players without winning a title – and this Heat team won’t merit such recognition, either, without taking home the Finals trophy.

“Our team was built for that,” James said. “We stress it every day, about building championship habits.”

Those habits disappeared during a four-week stretch that began in early March in which the Heat fell short repeatedly against quality opponents. The team lost away games to the Utah Jazz, Lakers, Orlando Magic, Thunder, Chicago Bulls, Indiana Pacers and Boston Celtics, who offered a 91-72 rout as an insulting climax on April 1.

At the time, Spoelstra experimented at center, starting Joel Anthony, Ronny Turiaf and Udonis Haslem on various nights. He got spotty play from Mario Chalmers and Norris Cole at point guard, forcing him to call more frequently on rookie Terrel Harris. Miami, which finished with an 18-15 record on the road, posted a 19-13 mark from March on.

“We needed to address our consistency and identity and make sure we were playing at a high level going into the postseason,” Spoelstra said. “Three weeks ago, we weren’t. It was a frustrating time for us. We’re not out of the woods yet.”

Even while cracks surfaced in various corners of the Heat lineup, James remained steadily spectacular. He averaged 27.1 points on 53.1 percent field goal shooting with 7.9 rebounds, 6.2 assists and 1.8 steals per game.

He said he has rediscovered his love for the the sport in his second season in Miami, while also taking on a more active leadership role. His play has ranged from jaw-dropping to surprisingly functional; he has helped mask the Heat’s primary rotational weaknesses at the point and center by improving his post-up game and running the offense when called upon.

“Last year was a tough year for him,” Wade said. “It was the first time he’s ever been out of Akron, Ohio. He was trying to figure things out. . . . He’s playing the game as one of the best players to play the game, [and he’s doing it] every night, consistently. . . . That’s the LeBron James we all know and love, and the LeBron James we wanted to play with.”

Wade, meantime, looked sluggish late in the season when he wasn’t sitting out to rest his weary body. That, however, worries absolutely nobody in Miami.

“We’re not concerned about him,” said shooting guard Mike Miller. “He’s got a different level that comes out in the playoffs, a special knack for that. We expect nothing less in the playoffs this year.”

Wade says he is ready to go. The test begins Saturday.

“A lot of teams are eager to get to the playoffs,” Wade said. “This season’s been a long short year. . . . Last year’s team went to the Finals. We’ll see where this year’s team stacks up compared to that team.”